Alternating current control system



12, w36. F. E. WELU 040,28

ALTERNATING CRRENT CONTROL SYSTEM original Filed Feb.Y 14, 193s Patented May l2, 1936 UNITED STATES PATENT OFFICE ALTERNATING CURRENT CONTROL SYSTEM Foster E. Weld, Newton, Mass., assgnor to The Gamewell Company, Newton, Mass., a corporation of Massachusetts 2 Claims. (Cl. 177-354) This invention relates to alternating current control systems and more particularly to arrangements responsive to signal impulses or current impulses generally, this application being a di- 5 vision of my copendng application Serial No.

656,664, filed February 14, 1933.

One .of the main objects of the invention is to provide in signaling systems of the type described in the above-mentioned copending application Serial No. 656,664 alternating current signal responsive devices which produce unidirectional current impulses, for the purpose of controlling with alternating current supplied signal loops receiving and repeating apparatus operative with direct current only, and to supply outer signal circuits as well as direct current operative signal responsive devices with electric energy derived from a source of alternating current.

In another aspect, the invention contemplates an electric system with a control circuit that is normally in a certain electric condition, and under such condition correspondingly aifects an associated reception or controlled circuit, any change in the condition of the control circuit causing a related change in the condition of the controlled circuit. The control circuit may, for example, be normally closed, when it causes no current now in the controlled circuit, but causing a controlled current iow when it is opened, or it may be normally open and cause the interruption of a current normally flowing in the controlled circuit.

A further object of the invention is to provide an electric system containing a circuit which is normally closed and supplied with alternating current and an associated circuit which furnishes unidirectional electromotive force Whenever the alternating circuit is interrupted.

Still another ob-ject of the invention is to provide a signaling system using alternating current in a signal dispatching circuit but (receiving station equipment being usually not well suited for operation with such current) permitting the operation of the receiving apparatus with direct current, and at the same time transmitting alternating current signal impulses originating in the dispatch circuit to the receiving apparatus in the form of direct current impulses.

These and other aspects and objects will be apparent from the following detailedwdescription illustrating the genus of the invention with reference to a concrete embodiment thereof. The description refers to a drawing, in which:

Fig. 1 is a circuit diagram of a practical embodiment of my invention; and

Fig. 2 is a simplied detail of the alternating current control arrangement of Fig. 1.

In Fig. 1, L denotes a control circuit or signal loop with a group of circuit control means, as for example signal formulating stations N herein also referred to as alarm boxes. Any suitable number of loops may be employed in order to provide the area served by the signal system with a sufficient number of alarm boxes, an additional loop L being shown in Fig. 1. According to the practice 10 common in re alarm systems, the embodiment of the invention herein described has normally closed loops, signals being formed by interrupting the loop circuits by suitable coding means. However, normally open loops in which signals are formed 15 by closing the loop circuits could be used With the present invention, as will become evident from the following explanations.

The loops L with alarm boxes N are supplied with alternating current of suitable voltage and frequency from supply busses |2|, |22, through supply transformers ||0, with supply primaries |51 and supply secondaries |56. Each loop has a line transformer T with control primaries'l5l, |52, also referred to as control and balancing inductances, respectively, having terminals |59 and |58 on either side of tap |50. An adjustable impedance |55, herein also referred to as balancing impedance, is provided which approximately reproduces the electric characteristics of loop L. 30 Secondary |56 of supply transformer ||0 is connected between tap and terminal |10 of the impedance |55, loop L with control means N is connected between terminals |10 and |59, and impedance between terminals |58 and |10. 35 It is apparent (especially from Fig. 2, which groups these elements in a somewhat simplified, but equivalent manner), that the electromotive forces of primaries |5| and |52 balance each other, provided that the primary windings and loop L and impedance |55, respectively, are electrically substantially equivalent, in which case no electromotive force is induced in secondary |60 of transformer T, so long as the loop is closed.

Secondary |60 supplies the input terminals |6|, |62 of rectifier bridges |63, |64 of conventional design, supplying output terminals |66, |61 and |68, |1|, respectively, with unidirectional current, if an electromotive force is impressed in secondary |60. In Fig. l, terminals |66, |61, |68 of 50 all line transformer circuits are denoted with these like numerals, whereas the fourth terminals of the loop have numerals |1I, |12, etc. All terminals |66 and |68 are joined by bus 8 and all terminals |61 are joined by bus 9, whereas terfil minals 1| |12, etc., are connected to corresponding line contacts 2, etc. of selector relay S.

The selector relay S is of the type commonly used as preselector in automatic telephone 1nstallations and may have any suitable conventional design. The selector herein indicated comprises a stepper magnet 39 with a vibrator arm 32, a vibrator contact 3| normally making con-` nection with the arm 32 (the contacts being bridged by a circuit suitable to suppress sparking) in series with the magnet, a number of line contacts i, 2, 3, etc., one line contact being provided for each loop, and a wiper 35 which is in well known manner mechanically or otherwise controlled by armature 32 so that it moves over the line contacts step by step so long as magnet 39 remains energized, thereby consecutively connecting the contacts with the selector lead 36. In well known manner, the wiper progresses always in the same direction and, having a sliding contact at each end, again touches the first line contact with one of these two sliding contacts after the other sliding contact has left the last line Contact.

The cut-oli relay C has a cut-olf magnet 8| controlling a stepper magnet switch 82 with stepper contact 33 and a change-over switch 84 with cut-off contact 85 and holding contact 86. Switch member 64 is connected through resistance |13 to one terminal of magnet 8|, and stepper switch member 92 is connected to the other terminal of 3|, and, together with that terminal, to one of the output terminals of rectier |14, to be described more in detail hereinafter.

In a manner similar to that shown and described in the United States Letters Patent Nos. 1,467,301 and 1,602,065, granted to Clarence E. Beach September 1l, 1923 and October 5, 1926, respectively, the register M has normally open contacts 295, 296 and a paper feed train, and switch operating devices which retain contacts 295, 266 normally open and close them effectively only for a short time just before the feed train terminates its run. As shown in Fig. 1, block 3| l, quickly turned by spring 3|? upon energiza.- tion of magnet 3|3, closes at that time the contacts during a period which is so short as to have no inuence upon the circuit, whereas, towards the end of the slow return movement of 3| it closes contacts 295, 296 for a time which is sufficient to effect the desired result which will appear hereinafter.

Stepper magnet 36 is connected between bus 9 and stepper magnet switch 82, which normally connects it with bus 8 through conductor 46, and also with one terminal of cut-off magnet 8|. The other side of the magnet 5| is connected, through resistance |13, to change-over switch 94 which connects it normally to wiper 35, through alarm circuit conductor 45. The holding contact 86 is connected to the positive terminal of aforenamed local rectifier |14.V The negative terminal of that rectier is connected through conductor 46 to the bus 8 and through said conductor 46 to contact 82 and magnet 8| as above described, and the input terminals are connected to the alternating current supply bussesA |2| and |22. Magnet 6| can be short circuitedby normally open contacts 295, 296 of the register M whose magnet 3| 3 is connected between conductors 45 and 46. Y The reception circuit A comprises reception circuit conductors 65 and 46 connected to wiper 35 and the negative terminal of rectifier 14 respectively, and signal repeating Vdevices such as tape recorders, gongs, or any other suitable recording, acoustic, or optic signal manifesting means, which are indicated at 59. The circuits supplied from the controlled rectiers |63, |64, |61, |68, etc. may be termed controlled reception circuits, whereas the circuit supplied from rectier E 14 will be referred to as holding circuit.

The arrangement shown in Fig. 1, especially suited for operation with alternating current, but in principle an adaptation of the circuit of Fig. 1 of the above-mentioned copending application Serial No. 656,664, with a cut-01T relay added and employing instead of the line relays E of that circuit what may be called, for want of a better term switchless alternating current re-l lays, constituted by control devices according to the present invention operates as follows: Under normal conditions, when the loops L, L', etc., are closed, the electromotive forces of the line transformer primaries l5 |52, supplied from busses |2l, |22, balance one another and no electrornotive force is induced in |69, so that the station circuit does not carry any current. Upon interruption of a loop, say L, connection between |59 and E16 is broken, |5| carries no current, and the electrcmotive force of |52 induces a current in the supply circuit of rectiiers |63 and |64, so that unidirectional electromotive forces appear across terminals |66, |61, and |68, |1|, re-

spectively. The unidirectional potential across -f busses 9 and 9 supplies current to circuit 8-46- 62-3i-32 36-9 which energizes stepper mag-` net 66, the latter advancing wiper 35 until it touches line contact l. At this moment, a circuit |688458 I-i 13-8 4--8 5 4 5 3 5-|-. |1 is closed, energizing cut-oir magnet 8| which attracts its armatures S2 and 86, opening the above traced stepper magnet circuit at 82, and changing member 84 from cut-off contact 85 to holding contact 86. rupts the stepping action of magnet 36, arresting the wiper at the appropriate line contact and establishing a holding circuit for cut-01T magnet Si from the negative terminal of rectifier |14, through 46-8-i13-84-86 to positive terminal of rectier |14, so that no other loop can interfere with the signaling loop L during energization of 8|. After loop L has nished its signal, that is, shortly before the feed train of register M has run down, contacts 295, 296 are closed, shortcircuiting magnet 8|, which thereupon releases members 82 and 66, restoring the circuit to normal condition. The resistance v|13 prevents short-circuiting of the rectifier |14 during such closure of contacts 295 and 296.

During the signaling period, signals are received at register M', or other apparatus, as 50, connected to the alarm circuit. Unidirectional current is furnished by the rectier bridge |14 for the holding circuit of relay C. In this manner, a signaling circuit supplied with alternating current exclusively is provided, which combines the advantages of signal loops energized with alternating current and of a repeater circuit operated with unidirectional current, without involving the use of relays and local supply batteries.

If any one of the loops, for example loop L, remains open indefinitely, the contacts 295 and 296 of register M' will vcause momentary deenergization of magnet 8| and during such deenergization of 8|, contacts 82 will close the circuit through magnet 30 and cause stepping of Wiper 35. If no other open loop circuit is found, wiper 35 continues to step around until it againiarrives at This action instantly interf contact I where it again stops and causes a second actuation of register M'.

This action is repeated continuously so long as loop L remains open, thus calling the operators attention to the faulty condition of the system, which can be rendered responsive to the sound loops by manually interrupting the rectifier output leads of the faulty loop.

It will now be understood that my new arrangement can be utilized for normally open control circuits. Assuming, for example, that in Fig. 2 the switch at L is normally open and that alternating current is continuously supplied at |51, the controlled circuit including secondary I, is normally supplied with current caused by the electromotive force induced in winding |52. Upon closure of the control circuit at L an electromotive force in |5| is added to that in |52, causing the electromotive force in secondary |60 to decrease or to disappear, which effect can be appropriately utilized to obtain desired functions in the controlled circuit including winding 60.

It will now be evident that the herein-described arrangement can be used in any signaling circuit employing normally open or normally closed signal initiating circuits supplied with alternating current and that it is useful not only in signaling installations but in every case where it is desirable to have a device Without switching elements, which effects a current change in a controlled circuit carrying either alternating current or direct current, upon a change in the current conditions in a controlling alternating current circuit.

It should be understood that the present disclosure is for the purpose oi illustration only and that this invention includes. all modifications and equivalents which fall within the scope of the appended claims.

I claim:

l. An electric signaling system of the character described comprising a source of alternating current; a plurality of signal loops each serially including signal initiating stations, a supply transformer secondary supplied from said source and a control transformer primary; balancing circuits connected to each of said supply transformer secondaries in parallel to said control primaries, each balancing circuit having a balancing primary coupled wi'th the respective control primary; controlled secondaries coupled to each pair of said primaries; rectifying means for each of said loops supplied from respective ones of said controlled secondaries; a direct current signal reception circuit including a signal manifesting means and a selector switch for consecutive connection of said manifesting means with respective ones of said rectifying means upon energize.- tion thereof by an abnormal signal loop; means for arresting said selector switch for connection of said manifesting means with said abnormal loop; holding means for maintaining said selector switch in arrested position; and a rectifier supplied from said source for energizing said holding means.

2. An electric signaling system of the character described comprising a source of alternating current; a plurality of signal loops each serially including signal initiating stations, a supply transformer secondary supplied from said source and a control transformer primary; a direct current signal reception circuit including signal manifesting means and a selector switch havin-g a stepping magnet for actuation thereof and a plurality of contacts arranged for consecutive connection thereof to said manifesting means; balancing circuits connected to each of said supply transformer secondaries in parallel to said control circuits, each balancing circuit having a balancing primary coupled with the respective coni trol primary; controlled secondaries coupled to each pair of said primaries; and two rectifying means connected with their input terminals in parallel to each controlled secondary, one of said rectifying means supplying said stepping magnet and the other being associated with said re ception circuit through connection to one of said contacts, the current induced in o-ne of said controlled secondaries upon signal initiation by changing electric conditions in the corresponding loop causing said rst rectifying means to energize said stepper magnet for actuation of said switch until it establishes connection of said corresponding loop to its contact in the manifesting circuit, for reception of signal impulses through said secondary, said other rectifying means and said contact.

FOSTER E. WELD. 

